The present invention relates to a centrifuge control system and method and, more particularly, to a control system and method for controlling the operation of a decanting centrifugal separator in response to variations in several operating parameters.
Decanting centrifuges are well known in the art and are designed to process a mixture of two constituents, usually a liquid and a solid, separating one from the other. These types of centrifuges feature a rotating bowl and a spiral screw conveyer disposed inside the bowl which rotates in the same direction as the bowl and at a different speed. The mixture, which for the purpose of example, will be assumed to be a liquid having relative fine solid particles entrained therein, enters the bowl and the centrifugal forces direct and hold it against the inner wall of the bowl in a "pool" while the fluid is displaced to one end portion of the bowl for discharge. The solid particles settle against the wall and are transported, or displaced, by the screw conveyor to discharge ports extending through the opposite end portion of the bowl for discharge. Typical applications of this type of centrifuge is in pulp, paper, and waste water treatments and for the removal of dirt, sand, shale, abrasive cuttings, and/or silt particles (hereinafter referred to as "solid particles") from drilling fluid after the fluid has been circulated through a drilling bit to lift the cuttings to the surface in an oil field drilling operation.
However, there are several parameters involved in the operation of a centrifuge, such as bowl speed and torque, conveyor speed and torque, fluid pump rate, fluid viscosity or dilution, and fluid solids content and properties. Since the operational goals of the centrifuge itself are fairly precise, it is important that the centrifuge be controlled so that its operation is optimized in response to variations in the above parameters. Also, the centrifuge itself can be operated in different modes in accordance with different design goals, such as maximum solids separation, maximum solids discard volume, etc., which requires further precise control. Therefore, what is needed is a control system of the above type which can maintain precise predetermined operational modes despite variations in the various operational parameters and design goals and which includes computer programs stored on computer-readable media that can be utilized to achieve these goals.
Also, in critical field operations utilizing the centrifuge, a sudden shutdown of the centrifuge due to breakage, mechanical failure, etc. can be disastrous. Therefore, what is needed in this respect is a control system of the above type which predicts eminent mechanical failure, modifies the operation of the centrifuge, and provides an advanced warning so that failure of the centrifuge can be minimized.